Pipeline Repair for an Oil & Gas Operator

Challenge 

In the second quarter of 2021, it was suspected that a client’s 4-inch MEG and CI pipeline was leaking fluid. In September 2021, it was confirmed that the pipeline was leaking at the client’s platform location following the deployment of an ROV.  

Due to metocean conditions, extensive marine growth on the riser, and limitations with ROV capability, non-destructive examination was not undertaken on the through wall defect area. As a result, the exact root cause and geometrical shape of the through wall defect and leak is currently unknown. 

Currently, the pipelines are operating with unmitigated corrosion and hydrate formation potential without the MEG and CI injection. From January 2022, production from the platform may require scaling back or to be shut-in– leading to lost production revenue for client until the MEG & CI import line is returned to operation. 

Services

Penspen provided engineering support for the identification and selection of repair solutions, preliminary engineering of the repair solution, and onshore and offshore engineering support for implementation. 

The service was split into 3 stages:

• Comparative assessment of the options
• Preliminary engineering of the favoured solution
• Installation of the final option.    

The comparative assessment process was used to identify potential options and eliminate un-feasible options. 11 scoring criteria was developed with weightings applied. These solutions would be compared against in a Multi-Criteria Decision Making (MCDM) model.  

The top 3 options in this evaluation would be passed through to the next stage. Once the solutions were selected, preliminary engineering and installation could commence and Penspen would provide the necessary support depending on which option was brought to this stage.  

Result

The final ranking output of the Comparative Assessment process determined that a new flexible riser was the most favourable solution followed by re-routing to a spare riser on the platform. The third best option was a localised repair (either a split bolted clamp or MorGrip) solution applied directly onto the existing riser. 

Following completion of phase 1 of the engineering, it was deemed that the replacement Thermoplastic Composite Pipe (TCP) flexible riser was the most suitable solution to return the MEG & CI import system to service. Phase 2 works focused on preliminary engineering for the installation of a new flexible riser. Penspen provided support on the design and installation of the new riser plus the tie in spools. 

The utilization of Penspen engineering services has provided the client with technical expertise and providing highly experienced management to suit the respective stages of the project. Penspen are now providing support for the permanent solution.